Fortification Friday: The optional, but useful, Glacis.

It’s Friday so let me continue to walk along the details of Mahan’s profile:


We’ve discussed the Parapet and the Ditch in detail. Now time to look beyond the Ditch to the structure Mahan placed to the front of the works – known as the Glacis.

The glacis is a small mound of earth raised in front of the ditch ; it is seldom used in field works, and is therefore not a constituent part of their profile.

Tag this as “optional.”  So if you were looking to cut down on the amount of dirt movements, you can skip the glacis.

Well not so fast.  Why have it in the first place?   Recall what I said earlier about the relation between the angle of the Superior Slope and the width of the Ditch.   Mahan wrote:

The superior slope is arranged to defend the crest of the counterscarp ; to effect which the fire should not strike below the crest, nor pass more than three feet over it ; otherwise, either the counterscarp would be damaged, or the assailed by stooping when near the crest would find a shelter. The inclination of the superior slope, however, should not be greater than one-fourth, nor less than one-sixth, that is, the base of the slope she uld be between four and six times the height. If greater than one-sixth, it would make the portion of the parapet, about the interior crest, too weak ; and if less than one-sixth, the ground directly in front of the work would not be so well defended ; more-over, as artillery cannot be fired at a greater depression than one-sixth, without injuring the carriage, this inclination of the superior slope serves as a check in rapid firing.

So we need to go back to the line I offered last Friday:


This depicts the desired angle, relative to points E (the Exterior Crest on the Parapet) and either point K or M (the crest of either the Counterscarp, if needed, the Glacis, respectively).  This was a critical measure for the fortification.  Let us dissect the profile a bit:


What Mahan said is that if bullets fired on a line from behind the Parapet would strike at a point beyond outer crest of the ditch, then it offered an uncovered space in front of the works.  Consider that a “shallow” angle between E and K.  That is depicted with the red line on the diagram above.  Such was a serious flaw the defender wished to avoid. However, if the line of fire offered a steep angle, that implied the defender had to raise up too much over the parapet (the blue line on the diagram).  And thus the Banquette was too high and needlessly exposed the defenders.  Oh, and also any artillery place on the Banquette might not depress to engage the enemy. The “just right” zone for this line offered an angle in which bullets fell directly on the crest of the Counterscarp, or just three feet below it.  That ensured the enemy was not granted a place to gain a foothold, short of the Ditch.  Furthermore, while in the Ditch the enemy could not engage the men on the Parapet.  If set “just right” the Ditch would become a place where the enemy could only pause to contemplate just how precarious the situation was (and perhaps start waving white flags). But nature rarely offers the engineer a “just right” solution.  So often there was a need to adjust nature to achieve that “just right” angle.  And the Glacis was that adjustment:

If, owing to the command, the fire should pass higher than three feet above the crest of the counterscarp, it would then be necessary to construct a glacis in front of the ditch. It must be so arranged that it can be swept by the fire of the work, and be commanded by it at least five feet.

Mahan defined that as the lines between the Crest of the Counterscarp (K), Crest of the Glacis (M), and  Foot of the Glacis (N). (Yes… no L, as it looked too much like an I).


There was no fancy names offered for these lines.  Let me, following some convention, arbirtrarily call the line between K and M (I’ll explain that K’ in a second) as the Interior Slope of the Glacis:


Clearly this had support the crest (M) at a height to achieve that “just right” angle.  But, as with the discussions of the slopes of the parapet and ditch, the desired angle of the slope was no steeper than that at which earth normally piles.  Otherwise it became a maintenance issue.

I’ll call the line from the Crest of the Glacis to the Foot of the Glacis  as simply the Exterior Slope of the Glacis.  Feel free to come back with a more proper term, if you wish.


The Exterior Slope, in keeping with the function of the Glacis, would lay on the same line as that from the Parapet’s Superior Slope.

But there was one other line to consider here, and where K’ comes in.


This is not labeled on Mahan’s diagram, it’s my convention.  But Mahan did discuss this line.  Just as with the Parapet and Ditch, were a Berm was often needed to off-load the weight of the piled earth, the Glacis often had to be placed away from the Ditch to prevent a maintenance problem.  So this was in effect another berm.

But this line of K to K’ had another desired purpose.  If desired for the defense, it could become an advanced Banquette of sorts.  Defenders on that section could delay, if not stop, attackers attempting to scale the Glacis.  Furthermore, the protection afforded by the Glacis would allow defenders to maneuver on the exterior of Ditch if needed.  Taking a term from more elaborate fixed fortifications, this was known as the Covered Way.

Overall, we might easily rate the Glacis as simply an option for those who had time and labor to expend making a work just a bit more formidable.  However, we must consider those angles – shallow and steep – between the Parapet and Ditch.  A well constructed Parapet might be undone by the lack of a Glacis.

(Citations from Dennis Hart Mahan, A Treatise on Field Fortifications, New York: John Wiley, 1852, pages 3 and 21.)


My advice to Loudoun’s BOS: Fund historical markers, memorials can come later

I’ve mentioned the concerns expressed here in Loudoun County with respect to the Confederate memorial on the courthouse square (here and here).   Most I have spoken with, locally. have called for additions to the courthouse lawn …  and not removal of any memorials. Last week, Leesburg Today ran a story noting an initiative at the county level toward that end:

York To Push For Slave, Union Memorial At Courthouse

It’s looking more likely a remembrance of slaves sold on the Loudoun County courthouse steps could be coming to Leesburg.

County Chairman Scott K. York (R-At Large) said Monday that he would ask his colleagues on the Board of Supervisors on Sept. 2 to support placing such a memorial on the courthouse grounds.

The commemoration could also note the history of Loudoun residents who fought for the Union army in the Civil War, York said, or that bit of history could be memorialized in another way.

The chairman also said he will ask the supervisors to approve a contribution of $50,000 in county funds toward the cost of the memorial or memorials. The money would be donated only after the rest of the fundraising was complete, York said, in the same way that the county dedicated $50,000 toward the creation of a Revolutionary War statue, which is scheduled be placed on the courthouse grounds this Veterans Day….

The article goes on to discuss an effort, backed by the local NAACP branch, to place a Virginia State marker at the courthouse:

Phillip Thompson, the branch’s president, said Monday that he was pleased with York’s proposal, but he also noted that a lot of work still would need to be done before any memorial comes to fruition.

He met with York and other county government and community leaders Aug. 18, and he said that the NAACP and the Friends of the Thomas Balch Library’s Black History Committee will aim first to ask the Virginia Board of Historic Resources to approve the placing of a state historical marker at the courthouse noting the slave sales and Underground Railroad recognition.

“That’s an easier initial push,” Thompson said of the silver-and-black markers, which are generally placed along the sides of roads….

Certainly a positive step forward in all regards.

However, I would offer some observations from my seat.  Some background for those not from Loudoun is in order.  The Revolutionary War memorial mentioned by York is the product of a long running project that began in 1999.  To put a memorial up, the project needed $325,000. Not until 2012 did the project reach it’s halfway funding mark.  In December 2013, the county voted a $50,000 grant, the same figure proposed by York for the proposed slave memorial, to complete the project.  And the project will reach fruition nearly two years later when the memorial is dedicated on Veterans Day later this year.

And that effort serves as a good teaching point.  The memorial is indeed something the county will be proud of in the future.  It will fill a role, noticeably lacking, in the county’s historical landscape.  But it required a decade and a half, significant fundraising efforts, and (what I have not covered for brevity) a lot of discussions.  My point?  Memorials are good things, but they require long gestation periods and generous resource allocations.  Furthermore, memorials might not have firm “grounding” in the community, leaving them less effective.

On the other hand, I like options offered in this case – historical markers.  In fact, I would prefer that the funds be offered as grants towards historical markers.  Grants… as in plural.

My role as a member of the Loudoun County Civil War Sesquicentennial Committee has given me some perspective on this.   Prior to the 150ths kicked off, there were twenty-seven historical markers, outside of those on the Balls Bluff battlefield, with substantial Civil War content.  During the sesquicentennial years, worked to place fifteen new markers in the county, an increase of over a third.  And there are two more “in the works.”  Of those markers, three (plus one of the pending markers) focused on unionist activity in Loudoun.  And three of the markers focused on wartime activity of slaves and free blacks, to include USCT.  That’s not counting the marker placed at the courthouse which, while trying to cram four years of wartime activity into 250 words, begins, “Before the war, the courthouse square was the location of slave auctions and militia recruiting activities.”

I don’t laud those achievements to say “our work is done.”  I bring those markers up to show, while progress has been made in public interpretation in the last five years there is much more to do.  For instance, we identified five other cemeteries which contained graves of USCT.  If we want to tell the complete story about Loudoun’s history, specific to the Civil War, and talk about slavery, then we should consider those sites for interpretation.

And that brings me back to that proposal from last week.  I’ve learned a lot in the last five years about how to use markers.  Likewise, I’ve learned some of the failings of memorials.  Not to say memorials are not needed.  Rather to say they are not always a good investment as compared to historical markers.  Going back to the Revolutionary War memorial, we see that will cost over $300,000.  Looking to the Mount Zion Cemetery marker featuring the USCT, that cost $2600.  The cemetery marker is part of a broader Virginia Civil War Trails system and thus is one in a larger, well-advertised, and established marker system.  And even more, the cemetery marker offers content which serves to educate where it stands.

I look at it this way – $50,000 would fund part of a memorial.  But $50,000 would go to fund almost twenty historical markers.  Those twenty markers would serve as direct educational products for the community.  If spent on such, that $50,000 would be an investment of sorts.  With placement those twenty markers could, by increasing community awareness and appreciation for the county’s history, pave the way for something substantial… perhaps on the courthouse lawn, though I’m thinking more so within the minds of the community.

Cavalry Logistics lesson – Carbine ammunition, parts were not universal

Monday being my day to discuss cavalry operations, and my opening steps on this convention being focused on ammunition expenditure, let us take up a logistical question in that regard.  Troopers went into action with a wider selection of arms over their infantry or artillery counterparts.  He often had the choice of using the saber, the pistol, or the carbine (or… for some of you… the lance!).  Of those, technology advances in the years running up to the war most improved the carbine.  I’ll touch upon the pistol and the saber at other times.  Today let us consider the carbine and what it was “fed” when used on the firing line.

For the most part, ordnance officers assigned to the infantry might focus on two calibers, .577- and .54-inch, unless issued some exotic import or new-fangled repeater.  But the ordnance officer supporting the cavalry had a headache to contend with.  Consider the list of popular cavalry carbines used in the war:

  • Spencer Carbine – .52 caliber brass cartridge
  • Sharps Carbine – .52 caliber linen cartridge
  • Burnside Carbine – .54 caliber brass cartridge
  • Smith Carbine – .50 caliber rubber cartridge
  • Henry Rifle – .44 caliber brass cartridge
  • Colt Rifle – .56 caliber paper cartridge
  • Muzzle loading rifled carbines – .54 caliber paper
  • Sharps & Hankins – .52 caliber brass cartridge
  • Maynard Carbine – .50 caliber brass cartridge
  • Joslyn Carbine – .54 caliber brass cartridge
  • Cosmopolitan (Union or Gwyn & Campbell) – .52 caliber linen
  • Hall Carbine, Percussion – .52 caliber paper cartridge
  • Merrill Carbine – .54 caliber paper cartridge
  • Ballard Carbine – .44 caliber brass cartridge
  • Gallager Carbine – .50 caliber brass cartridge
  • Gibbs Carbine – .52 caliber linen cartridge
  • Starr Carbine – .54 caliber linen cartridge

Again, this list is just the “basic” offering. We could spend days identifying more of the imports, exotic limited-use, various impressed weapons, or modified types.  I’ve not included shotguns, as those being impressed civilian arms were not of any standard military caliber.  As it was, any definition of “standard military caliber” as it referred to cavalry carbines would stretch the concept of the word “standard.”  Even where the caliber measure matched, the type of cartridge or even the type of ignition (percussion cap, percussion disk, Maynard tape, or on the cartridge – rim fire or center fire) differed.  So while the infantry might just request “ammunition”, a cavalry formation had to be picky.

This is, of course, nothing new to the student of Civil War cavalry.  Many will recall the armament of Buford’s division on the first day of Gettysburg – a mix of Sharps, Smiths, Burnsides, and Sharps & Hankins.  After a full day of action, each formation required resupply from their own trains.  None could borrow from the other.  And certainly none could draw from the infantry.  But that is one battle – indeed one day of one battle – and not a campaign.  Field formations were not supplied for just one “mad minute” of battle, but rather stocked for a series of actions.

What would make sense, from a logistical standpoint, would be some uniformity to the issue of carbines.  But as with much in life, what starts as a simple, practical solution would break upon the rocks of reality.  From the start of the war, units were equipped with what ever was available.  New equipment was issued when supplies and situation permitted.  Still, even at war’s end the Federal troopers had a mix of Spencers, Sharps, Burnsides, and Smiths.

Beyond just the “square peg in round hole” problem, the variance of ammunition carried other implications.  Consider that a Sharps linen cartridge weighed a little less and was packaged differently than a Spencer brass cartridge.  A standard Sharps round weighed 533 grains.  A Spencer round weighed 549 grains.  One by one, the difference is not significant.  But multiply that difference by thousands and suddenly there are planning factors to consider.

Convert grains to pounds here.  One pound is 7000 grains.  So do all the math and we find 1000 rounds of Sharps cartridges weighs a shade over 76 pounds.  The same number of Spencer rounds weighed just under 78.5 pounds. And that is not counting packing materials and the wood crate used to transport the bulk, which should be similar between the types.  Let’s say that resupply requirements call for 200 rounds per trooper on the supply wagons.  For an 80 man troop, that’s a difference of forty pounds when considering Sharps vs. Spencer.  Forty pounds does not sound like a lot when balanced against the typical army wagon, which could carry 2,800 pounds.  But continue to extend those forty pounds from troop to troop, up to the regimental and brigade level.  By the time the pounds accumulate up for a three squadron regiment, the difference is close to 500 pounds.  By the time the figures are complied for a full brigade, we have nearly a wagon-load difference between a Sharps-equipped unit over a Spencer-equipped unit.

Even more to the point, what YOU would carry.  Eighty rounds of Sharps ammunition weighed about six pounds.  Eighty rounds of Spencer ammunition weighed four ounces more.  Again, not a lot when you first think about it. But that’s four ounces carried around all day.  And four ounces of “bullet” carried in stead of four ounces of something else… like water or food, for either horse or man.  How many calories in four ounces of hardtack?

And that four ounces only accounts for the rounds themselves.  Troopers with Spencer carbines often carried additional magazine tubes and carriers.  So add more than just those four ounces to the amount of displaced hardtack.  Are you getting hungry yet?

Another under-appreciated factor with these carbines is repair parts.  Again, the infantry leaning on a lot more standardization (though not even close compared to today’s armies), the ordnance officer for the foot soldiers could keep the number of line items needed to a minimum.  For the cavalry, every single one of those carbine types required a different set of non-interchangable parts.  Due to the advanced nature, for the time, of the carbine, there were more moving parts that might break.  And again, none of which were standard infantry rifled-musket parts.

Yes, these shortfalls might have been resolved by adopting a standard carbine for mass production (as was done with the Springfield Model 1861 rifle during the war for the infantry).   But which one?   Sharps, which was established at the start of the war?  Spencer repeater, with its tactical advantages?  Or the Smith or Burnsides, which received complaints about reliability?  The reality was none of these types, or the lesser used weapons, was refined to the point that mass production was an option.  So the Civil War carbine was very much a “what we have” issue.  And unfortunately that was a regiment-by-regiment, if not trooper-by-trooper, issue.

And with that issue of carbines, the cavalry commander had considerations beyond what his infantry counterpart usually encountered.   The trooper’s ability to maintain a fire line relied upon many more question marks concerning ammunition and even the ability of the weapon to perform.